"Today, we're happy to make available a developer preview of the Native Client SDK - an important first step in making Native Client more accessible as a tool for developing real web applications. When we released the research version of Native Client a year ago, we offered a snapshot of our source tree that developers could download and tinker with, but the download was big and cumbersome to use. The Native Client SDK preview, in contrast, includes just the basics you need to get started writing an app in minutes."

Actually, since NaCl is open source, it can be compiled for Haiku too.

NaCl is kind of like a sandboxed OS inside an OS... providing native compiled x86 (or ARM) code that can run on any OS that NaCl has already been ported to.

There was already a suggestion to port NaCl to Haiku, but nobody seemed interested at the time, so it hasn't been attempted. In theory, if it was ported to Haiku, then any NaCl apps would be runnable in Haiku without a recompile, assuming they were run on the same architecture (x86 or ARM) that they were compiled for.